Computer Program and Method for Detecting and Predicting Valve Failure in a Reciprocating Compressor

Embodiments of the present invention provide a method implemented by a computer program for detecting and identifying valve failure in a reciprocating compressor and further for predicting valve failure in the compressor. Embodiments of the present invention detect and predict the valve failure using wavelet analysis, logistic regression, and neural networks. A pressure signal from the valve of the reciprocating compressor presents a non-stationary waveform from which features can be extracted using wavelet packet decomposition. The extracted features, along with temperature data for the valve, are used to train a logistic regression model to classify defective and normal operation of the valve. The wavelet features extracted from the pressure signal are also used to train a neural network model to predict to predict the future trend of the pressure signal of the system, which is used as an indicator for performance assessment and for root cause detection of the compressor valve failures

Changes in risk behaviours and prevalence of sexually transmitted infections following HIV preventive interventions among female sex workers in five districts in Karnataka state, south India

OBJECTIVES: To examine the impact of a large-scale HIV prevention programme for female sex workers (FSW) in Karnataka state, south India, on the prevalence of HIV/sexually transmitted infections (STI), condom use and programme coverage. METHODS: Baseline and follow-up integrated biological and behavioural surveys were conducted on random samples of FSW in five districts in Karnataka between 2004 and 2009. RESULTS: 4712 FSW participated in the study (baseline 2312; follow-up 2400), with follow-up surveys conducted 28-37 months after baseline. By follow-up, over 85% of FSW reported contact by a peer educator and having visited a project STI clinic. Compared with baseline, there were reductions in the prevalence of HIV (19.6% vs 16.4%, adjusted odds ratio (AOR) 0.81, 95% CI 0.67 to 0.99, p=0.04); high-titre syphilis (5.9% vs 3.4%, AOR 0.53, 95% CI 0.37 to 0.77, p=0.001); and chlamydia and/or gonorrhoea (8.9% vs 7.0%, AOR 0.72, 95% CI 0.54 to 0.94, p=0.02). Reported condom use at last sex increased significantly for repeat clients (66.1% vs 84.1%, AOR 1.98, 95% CI 1.58 to 2.48, p<0.001) and marginally for occasional clients (82.9% vs 88.0%, AOR 1.22, 95% CI 0.89 to 1.66, p=0.2), but remained stable for regular partners (32%). Compared with street and home-based FSW, brothel-based FSW were at highest risk of HIV and STI, despite high levels of reported condom use. CONCLUSIONS: This large-scale HIV prevention programme for FSW achieved reductions in HIV and STI prevalence, high rates of condom use with clients and high rates of programme coverage. Improved strategies to increase condom use with regular partners and reduce the vulnerability of brothel-based FSW to HIV are required

Fatigue behavior of a hybrid particles modified fiberglass/epoxy composite under a helicopter spectrum load sequence

ABSTRACT The fatigue life of a glass fiber reinforced plastic (GFRP) hybrid composite containing 9 wt.% of rubber microparticles and 10 wt.% of silica nanoparticles in the epoxy matrix, under a standard helicopter rotor spectrum load sequence was determined and observed to be about three times higher than that of GFRP with unmodified epoxy matrix. The underlying mechanisms for the observed improvements in spectrum fatigue life of GFRPhybrid composite are discussed. Recently, we have observed that the hybrid GFRP composite containing 9 wt. % of micron-rubber and 10 wt. %of nano-silica particles in the epoxy matrix exhibit enhanced constant amplitude fatigue life by about eight to ten times over that of GFRP composite with unmodified epoxy matrix INTRODUCTION EXPERIMENTAL Materials and Processing The complete details of materials used and the processing employed to manufacture the GFRP composites can be found in Manjunatha et al wt.% of CTBN rubber in the final resin, were all individually weighed, degassed and mixed together and a stoichiometric amount of curing agent. The atomic force microscope (AFM) phase image of the particles modified bulk epoxy polymer is shown in The silica particles of about 20 nm in diameter were somewhat agglomerated to give a &apos;necklace-type&apos; structure with an average width of about 1 µm. The resin mixture was used to prepare the GFRP composite laminate by the &apos;Resin Infusion under Flexible Tooling&apos; (RIFT) technique The mechanical properties of both GFRP-neat and GFRP-modified composites are shown in Fatigue Testing Fatigue tests on both the GFRP-neat and GFRP-modified composites were conducted under a standard helicopter rotor spectrum load sequence, HELIX-32 shown in Spectrum fatigue tests were performed on GFRP composites with different reference stress levels ranging from 125 MPa to 200 MPa. The spectrum load sequence block with specific reference stress was repeatedly applied to the test specimens until failure and the fatigue life, expressed as the number of blocks to failure, was determined. The test specimens of size 150 mm x 12 mm x 2.6 mm with end-tabs were employed for the spectrum fatigue tests. All the tests were conducted using a computer controlled 25 kN servo-hydraulic test machine. When the specimen failed in-between any block, the fraction of the block completed was determined as the ratio of the number of reversals applied until then to the total number of reversals in the block. 5 The stiffness variation of the specimen subjected to spectrum fatigue loads was determined during the test as a function of the number of applied load blocks. Whenever stiffness measurement data were required, the fatigue test was intermittently stopped, a load cycle with σ max = 0.5 σ ref and stress ratio R=σ min / σ max = 0 was applied, the load, displacement data was obtained and analyzed. Considering the large number of load cycles in one block, insertion of this one cycle was assumed not to alter the fatigue damage in the material significantly. For the purpose of comparison, the normalized stiffness of the specimen was defined as the ratio of measured stiffness at any given time to the initial stiffness (obtained before application of the first spectrum load block). For one particular test with σ ref =160 MPa, the specimens were dismounted at the end of the application of one complete load block and photographs showing matrix cracks were obtained, as explained in Manjunatha et al. RESULTS AND DISCUSSION The spectrum fatigue life determined for both the GFRP-neat and GFRP-modified composites under the HELIX-32 load sequence at various reference stresses is shown in The fatigue failure mechanisms under cyclic loads in polymer composites involve The stiffness loss in &apos;stage I&apos; and &apos;stage II&apos; results primarily from matrix cracking &apos;stage III&apos; [25] which lead to an improvement in the spectrum fatigue life of the GFRP-modified composite. It is to be noted that the fatigue life enhancement is about eight to ten times under constant amplitude loads at stress ratio, R =0.1 CONCLUSIONS Based on the results obtained in this investigation the following conclusions may be drawn: 1. The addition of 9 wt.% rubber micro-particles and 10 wt.% of silica nanoparticles to the epoxy matrix of a GFRP composite (i.e. to give the GFRPmodified material) enhances the fatigue life under the HELIX-32 spectrum load sequence by about three times. 8 2. The stiffness degradation of the GFRP-neat composite is more severe than that of the GFRP-modified composite during the fatigue loading. The suppressed matrix cracking and reduced crack and delamination growth rate in the modified epoxy matrix of the GFRP-modified composite enhances the fatigue life under spectrum load sequence. ACKNOWLEDGEMENT

An integrative Raman microscopy-based workflow for rapid in situ analysis of microalgal lipid bodies

Additional file 1. Schematic diagram of Raman imaging technique

Characterization of Drug-like Chemical Space for Cytotoxic Marine Metabolites Using Multivariate Methods

In the last few decades, marine metabolites have been exploited to find commercially viable products in several areas. In this article, molecular descriptors [log P, mass, total polar surface area (TPSA), H-bond donor, H-bond acceptor, and the number of rotatable bonds] for the marine-derived cytotoxic metabolites were calculated and compared with marketed anticancer drugs to understand their position in the drug-like space. Marine-based cytotoxic metabolites are divided into highly toxic (HT) and moderately toxic (MT) classes. The marketed anticancer drugs complied well with Lipinski’s rule of five for all molecular descriptors. The majority of HT and MT metabolites complied solely with H-bond donors and a number of rotatable bonds with the Lipinski cutoff values. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were also performed using 73 molecular descriptors on an ensemble of highly cytotoxic or moderately cytotoxic marine metabolites and the marketed reference drugs. The HCA results showed that 12% of marine metabolites clustered with the marketed anticancer drugs and many of them had structural scaffold homology. The PCA results revealed the presence of a clear distinction between the cytotoxic marine metabolites and the marketed anticancer drugs. Results indicate that mass, TPSA, and log P are the vital parameters and the careful optimization of these parameters for marine cytotoxic metabolites may generate more meaningful anticancer candidates in the future

Optical Properties of Ce3+ in Self-Assembled Strontium Chloro(hydroxy)apatite Nanocrystals

Strontium chloroapatite nanocrystals (nc) of size in the range 10-100 nms have been prepared by an aqueous colloidal method. In this preparation, hydroxyl (OH-) ion contamination having profound dependence on the preparative conditions (in particular pH) could not be avoided. The hydroxyapatite phase (at pH ) 8) resulting from this contamination seems to exhibit some self-assemblage properties that may be electrostatic in nature. Optical data (based on UV-visible and fluorescence studies) show that the 2FJ ground state of Ce3+ as a dopant in these nanocrystalline apatites undergoes considerable modification arising from cross-relaxation between the Ce3+ ground state and hole states of the host matrix created near valence band edge